There are many applications requiring very low cost coin acceptors such as amusement games, small vending machines and the like. Generally these applications are extremely price sensitive and cannot afford the cost of electronic coin acceptors. These applications generally do not require the payback of change. Hence, they do not require coin changers which are very expensive (hundreds of dollars for the lowest end product). In most cases, this market is served by mechanical coin acceptors which are very inexpensive but suffer from frequent failures due to the number of moving parts used. Electronic coin acceptors have also been used, but most of these are settable for only a single coin type. These electronic coin acceptors are significantly more expensive than the mechanical acceptors and if more than one coin type is required, multiple units need to be used. Of course, higher end coin acceptors are available usually at significantly higher prices as the recognition technology involves multiple sensors to determine multiple parameters of a coin. In these cases, the acceptors are designed for a high level of discrimination and false coin rejection.
Traditionally, electronic coin recognition has depended on inductive circuits involving multiple coils mounted with great precision along the path the coin is expected to roll. Additionally, it is well known in the art to use two coils, one on each side of the coin path, to measure such parameters as the thickness of the coin. The cost of these components are relatively high, and in combination with the cost of the supporting electronics required to drive these coils, this technology is not suitable for the mechanical coin acceptor replacement market.
As discussed above, the current technology is such that in order to obtain additional parameters of the coin being tested, additional sensors are required. Multiple parameter measurements without adding additional sensors have been disclosed in the art, but not without penalty. These solutions require customized inductive pot cores or increased electronic hardware costs. Neither of these options allows this class of solution to offer a suitable mechanical coin acceptor alternative.
The prior art discloses a number of optical solutions to the coin recognition challenge. These solutions have not been commercially successful since the resolution of the measurements are not sufficient to allow the required coin discrimination and false coin rejection required even in the most benign of applications. An example is the separation of United States (US) dimes and pennies. The diameter difference between these two coins is about 6%. This separation is reduced by the tolerance variations of each of the coins, the resolution of the measurements, coin bounce and the like. In order to achieve a high resolution of dime acceptance, a number of pennies are likely to be accepted as a dime.
The acceptance rate of coins also depends on having the coins rolling or sliding smoothly as they pass the measuring sensors. There are a number of techniques used to help achieve this coin control. It is known in the art to use snubbers to absorb the energy from the coin in an effort to have the coin continue along its path with a minimum of bounces and at a relatively constant speed. Unfortunately, these snubbers have been made from ceramic materials or formed metals, both of which are relatively expensive. Additionally, the effects of the snubbers are often determined by how well these components are mounted to the coin paths. Of course any bounce in the coins or speed variations in the coins as they pass the measuring sensors will result in errors in the measurements taken. These errors are a significant source of the variations seen for any given measurement and result in a wider range of sensors readings that must be included to ensure a high acceptance level.
To further add to the challenge of achieving a high acceptance rate of desired coins while rejecting similar sized but lower value undesired coins (such as pennies and Canadian coins in the US, for example), many higher end coin acceptors include material sensors to make these distinctions. These material sensors are typically additional inductive coils which add cost and complexity to the coin acceptor.
Another requirement of coin acceptors is to prevent “stringing” as a cheat method. Stringing is the technique whereby a string or tape is attached to the coin. When the coin passes through the sensors and is correctly credited, the string or tape is pulled to withdraw the coin through the entry point. There are a number of techniques in the current state of the art to prevent “stringing”. Most of these involve the use of mechanical devices to catch the string or trap the coin if someone tries to pull it back. Most of these techniques again require additional components to achieve this function.